1. Field of the Invention
The invention relates to RF plasma processing apparatus, and more particularly to improved apparatus for RF sputtering deposition and etching of dielectrics and/or metals.
2. Description of the Prior Art
The fundamental process of sputtering, involving exposure of the material to be sputtered to bombardment of ions in a suitable pressure gaseous glow discharge and thereby causing the material to be impact-eroded and deposited upon an object to be coated, is known in the art. The sputtering of metallic substances can be accomplished by employing either direct-current excitation as disclosed in U.S. Pat. No. 4,576,700 to Kadokura et al, or radio frequency (RF) alternating-current excitation applied to the metal target electrode as disclosed in commonly assigned U.S. Pat. No. 4,647,361.
The successful application of the basic process of sputtering to dielectric materials, requiring the application of only RF alternating-current excitation to a metal electrode that adjoins the dielectric target, also is known in the art as disclosed in commonly assigned U.S. Pat. No. 3,617,459 to Logan and in U.S. Pat. No. 4,399,016 to Tsukada et al.
The fundamental process can also be used for selectively etching materials by the use of an RF voltage to form the plasma, in conjunction with an etchant gas as disclosed in U.S. Pat. No. 4,422,897 to Horwitz.
There has been an effort to increase both sputtering efficiency and sputtering productivity in systems with low-yield sputter materials Al.sub.2 O.sub.3, for example ) and the necessity to maintain substrate temperature below 100.degree. C., but these efforts have met with limited success up to the present. For example, an increase in the size of the electrodes to increase the batch capacity resulted in a decrease in the RF impedance to ground, thereby lowering the sputtering efficiency. The above-mentioned Logan et al patent discloses a variable impedance which can be tuned to enhance the sputtering quality by controlled resputtering during deposition. However, there is a limitation as to the resputtering voltages attainable at the substrate within such prior art systems.
The prior art has not shown a plasma processing apparatus which exhibits a wide range of resputtering, substantially improved RF power transfer to the plasma, and increased sputtering productivity simultaneously. In addition, the prior art has not shown a plasma processing apparatus which exhibits both high sputtering efficiency and substantial improvement in the deposition/etch uniformity across a large batch of substrates.